On 23.09.2006 23:12:06 TomᚠStudva wrote:
> Hi developers,
> 
> We are using FOP as rendering engine for FO in wysiwyg xml editor
> http://sourceforge.net/projects/euromath2. When opening about 40 page fo
> document, the editation is ugly slow. We can track changes in source
> document(also in case using XSLT), but  there is a principal error, because
> we don't know how to update the FOP produced trees, so new FOP is created to
> layout document after change and further render by Draw2d (we implemented
> some basic renderer composed of Draw2D Figures, which are organized into
> tree). 
> 
> I' ve also profiled our application on such big document, from typing to
> update of screen and found out, than FOP consumes 1/3 of processor time,
> that is too much if we optimize anything but not FOP- it takes on good PC
> about 10 seconds, so FOP 10/3 = 3sec. 
> 
>  
> 
> So, is there possibility to update the FOP produced trees according to
> change in XML (to use it in editor manner, not only rendering engine)?

No, FOP has not been designed to be used as a backend of a WYSIWYG
editor like EuroMath2. That's a new requirement/wish. We'd have to find
out if and how FOP can be changed to fulfill it. At any rate it's an
expansion of the project scope which could be subject to a project
decision depending on how extensive the necessary changes can become.

> Or if not, is there possibility to recycle FOP PageSequence which haven't
> changed?

Not at the moment, maybe with some hacking. It's not just the
page-sequence that would have to be recycled. You'd have to find ways to
keep the unchanged page-sequences in memory and that includes not only
the FO tree but also the area tree. However, changing a page-sequence in
the middle might invalidate later page-sequences.

> And last, is there option to speed up FOP generally, by lowering output
> quality or something?

Not by lowering the output quality, no. You can help by profiling and
optimizing FOP and you can make sure the editor only generates the
minimal FO content to produce the right document. Many editor generate
much too much (redundant) content not making use of property inheritance.
That can have an influence on performance.

You're welcome to help us improve FOP to better match the requirements
of EuroMath2. I'm pretty sure we currently don't have the resources to
help you much in this direction. We can give you pointers and we can
help you figure out what needs to be changed.

Please note this is my take on the situation and may not reflect the
opinion of the whole community.

I didn't know of EuroMath2 before your post. If I interpret this
correctly it is a content editor rather than an editor to create XSLT
stylesheets.

I've also taken a peek into your wishlist. I don't think you can
currently find any open source FO implementation that is better suited
for EuroMath2. Concerning the "partial FO rendering possibility": It
might be possible to come up with a way to render, say, only a single
fo:block-container with relatively little effort. This might have the
possibly interesting side-effect that we could write a plug-in for Batik
to render FO content within an SVG. :-)

Jeremias Maerki

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